W: Oh perfect, another piece of equipment that takes up lots of room.Don’t you think we have enough equipment to carry on our camping trips?
M：I know what you’re thinking,but if I find something that is both lightweight and useful,I think it’s worth having.This piece of equipment fits both those categories.
W：Well, how small is it?
M：It’s about the size of a pen!Just like the one you would use to write a letter.
W：Wow! I’m surprised.That’s pretty small. But how good is it at filtering the germs out of lakes or stagnant ponds?
M：It’s wonderful! It takes all the germs out of the water.(2)____________________________________________.
W：That’s amazing! But what if the water has dangerous chemical pollution in it?
M：Well, that’s different.The filter can’t remove dangerous chemicals or salts because the filters are not designed for that.To remove chemicals from the water would require a very sophisticated filter.It would be easier to boil the water and collect the steam if you were in that situation. But when you think about it,that’s not the major concern when you are out hiking in the wilderness. (3)__________________________________, ,but it probably has dangerous bacteria from all the animals that live near the water.
W：I guess you did find a good piece of equipment.